Androgens stimulate the rate of beta-glucuronidase synthesis in mouse kidney. In addition, the potentiating effects of synadrogenic progestins result in an increase in the rate of enzyme synthesis, whereas inhibitors of androgen action decrease synthesis. In addition to beta-glucuronidase, four new proteins were identified in mouse kidney which increase with androgen treatment. Androgen binding protein (ABP) was isolated from rat testis and epididymis. Both of these proteins have a similar subunit structure when analyzed by SDS electrophoresis and peptide maps. There is microheterogeneity of androgen binding protein in the testis. This micropheterogeneity changes as ABP moves from the rete testis and passes through the epididymis. Studies of protein carboxylmethylase indicated that this enzyme was high in rat testis. Recent studies indicate that this enzyme is also present in spermatozoa and that it is located primarily in sperm tail. These observations support the previous suggestion that protein carboxylmethylase may be involved in sperm motility.